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Numerical simulations of particle deposition on super-heaters

This study focuses on particle inertial impaction in numerical simulations of particle deposition on super-heaters. The study does not consider thermophoresis, eddy diffusion, or Brownian motions. The simulations are done using Direct Numerical Simulations (DNS) without modeling or filtering, resolving all space and time scales, including the boundary layer around the cylinder. The impaction efficiency and rates are analyzed for various Reynolds numbers and particle sizes. The study concludes that DNS is essential for resolving the boundary layer, and particle impaction is influenced by Reynolds number and particle size.

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Numerical simulations of particle deposition on super-heaters

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  1. Numerical simulations of particle deposition on super-heaters A fundamental study Oslo, 2010.02.16 Nils Erland L. Haugen

  2. Introduction • Main focus: Particle inertial impaction • No thermophoresis, eddy diffusion or Brownian motions • This work has been done under the NextGenBioWaste project

  3. Simulations • Direct Numerical Simulations (DNS) are used • No modeling • No filtering • All space and time scales are resolved • Including the thin but important boundary layer around the cylinder • The Pencil-Code • 128 CPUs

  4. The Stokes number

  5. Particle impaction (0.01<St<0.3) Re=420 Re=20 Re=6600

  6. Front side impaction efficiency

  7. Front side impaction efficiency Classical impaction Boundary stopping Boundary interception

  8. Back side impaction

  9. GKS (MSWI in Schweinfurt, Germany) Super heater fluid specifications:

  10. GKS particle impaction Re=20 Re=1685 Re=420

  11. Impaction efficiency as function of particle diameter Three orders of magnitude

  12. Impaction rate Particle mass density pr. bin (independent of bin size)

  13. Conclusion • DNS is required in order to resolve the important boundary layer • Both the front and the back side impaction depends strongly on Reynolds number • The total mass impaction rate at the super-heater of the GKS plant is totally dominated by particles larger than ~30 microns

  14. Turbulence

  15. Single cylinder vorticity Re=20 Re=6600 Re=420

  16. Particle impaction (0.4<St<40) Re=420 Re=20 Re=6600

  17. Alternative to the Stokes number

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